I'm starting to realize how unbalanced this game is, and its gotten to the point where I might have to edit my initial review of the game.
In the beginning, there were only SSR and SSR+ being the two highest ranking girls you can get. Nevermind not being able to upgrade the lower ranks (e.g changing an R to an SR with enough copies) and level-capping them thereby making them completely useless (which in itself is a BIG turn-off for me and just a general issue for many reasons). Some of these SSR/SSR+ ranks couldn't (and still can't) be unlocked through normal ways and instead are locked behind events/paywalls.
Now, after a bajillion updates and a few anniversaries, we have UR and MR ranks, which are more powerful than the SSR/SSR+ and are EXCLUSIVELY locked behind events/paywalls. So what you now have is a game that latches onto the FOMO gimmic and becomes even more whale exclusive than it was before. So if you're a free player, and try to summon UR/MR ranks via events, and don't succeed, you're stuck with blueprints that you're never going to use until whenever the devs decide to be generous enough to open up that specific character event again.
In fact, this is starting to remind me of "Run! Goddess", and I already got done saying I quit that game after dealing with their crap and the way they do characters. I've been on and off with Idle Angels, but the new stuff is repelling me away more than keeping me on. If it keeps up, I'll have to quit this forever too.